I have never been in the situation, but I doubt that proximity is the only issue. Judging only from the news reports, it appears that there was an active shooter moving through a crowd, and it is easy to imagine that individuals in the crowd were moving in unpredictable directions. I don't know how one could get a safe shot in such a situation without being at contact distance and having a combination of weapon and ammunition that gave you a high degree of confidence that you would not have a through-and-through round that endangered others.

Situations like that seem like a no-win to me. If I understand Double-Naught's point correctly - that there are situations in which we may have need of responses other than firearms, and that they can have some success if employed with rational thinking and a commitment to positive action - is a point well worthy of consideration.